In the United States, about 21.2 million people currently have limitations in basic physical activities, such as walking, climbing stairs, carrying, or lifting. Over 100 million people with physical disabilities use wheelchairs for their primary mobility in the world, and yet less than one percent of these people have access to a wheelchair. The use of wheelchairs has increased for several reasons: birth defects, accidents, debilitating diseases, and advanced age. Based on the report of World Health Organization, more than 29,000 people annually have unexpected injuries. An estimated 250,000 to 400,000 people have spinal cord injuries or spinal dysfunction. Therefore, experts anticipate that the need for wheelchairs worldwide will continue to increase, up to 22 percent over the next 10 years.
While the number of wheelchair usage in increasing, it has created an increased demand for wheelchairs has led to an expanded market that continually offers better wheelchairs and seating systems. Based on innovations in technology, people are living longer, and are participating at higher rates. The demand to maintain an active lifestyle is also presented among people with disabilities. Wheelchair technology is integral to maintaining on active life style for individuals with a disability. Wheelchairs allow people with disabilities to have enhanced function, improved independence, and access to home and community. The lack of wheelchair is the main cause of limited participation to people with spinal cord injuries, so the wheelchairs are most important mobility of them. After their injury, wheelchair users accept their disabilities and consider a wheelchair as an extended body. Wheelchairs are critical components to meet users' expectations, preferences, physical needs, and functional requirements.
Different types of wheelchairs have different comfort and ergonomic ratings, as the different wheelchairs have different qualities. A wheelchair having more adjustability received higher ratings on comfort and ergonomics compared to a wheelchair with minimal adjustability. Since most wheelchair users spend half of the day sitting. Therefore, as the supply of manual wheelchairs increases, the demand of making them safer, more effective, and more readily available is necessary with wheelchair users' needs/adjustability.
Secondary injuries (e.g., repetitive strain injuries, pressure sores and so on) are of particular concern for those who use wheelchairs as their primary means of mobility. Since a wheelchair is an extension of the user's body, even the best fit wheelchair may not prevent the secondary injury. Pressure ulcer is one of the secondary injuries. The pressure sore occurs higher when people stay in a confined chair, have inability to move, have poor nutrition, and have lowered mental awareness. People with disabilities have difficulty changing positions and altered sensation, so they are at risk of pressure sores when they are not provided by adequate pressure-relieving mechanisms. Products and services need to be available to prevent or delay these conditions as they provide demands.
It is a challenge to recommend a particular wheelchair because wheelchair configuration influences wheelchair users' comfort, possibilities of transfer, efficient propulsion and so on. Wheelchairs usually have adjustability with axle position, seat depth, height of the footrests, tilting angle and reclining angle. Among those of adjustability, changing height of the footrests or changing backrest angles is only trial and error to avoid pressure sores as prevention of a secondary condition. According to the study of effect with changing tilt and seat-to-backrest angles by shoulder during wheelchair propulsion, seat angle could be standard for the user comfort and pressure modulation without risk of overuse shoulder injuries for alleviating pressure. As the backrest provides pressure relief, it is an essential part of wheelchair configuration.
Differences in postural alignment and shoulder flexion range are observed between wheelchairs with standard configurations and wheelchairs with posterior seat inclination and a low backrest which was set perpendicular to the floor. The wheelchairs with posterior seat inclination and low backrest set perpendicular to the floor give significantly more active upper extremities' flexion. The backrest does support the lumbar spine for maintenance of anterior pelvic tilting. And, the angle of backrest gives the wheelchair users spaces for posterior tilting.
In addition, the backrest protects and supports the spine which is one of the most important structural parts in the body. Because the weight of the upper body is sustained through the spine to transfer into the limbs, the spine is an imperative structural component. Therefore, the protection or support of the spine is essential. In many cases, wheelchair users have insufficient muscle strength to support and control the spine, so the spine tends to be bent and deformities of the spine are caused by forces of gravity. When the wheelchair backrest does not provide proper postural supports to a wheelchair user, the problems of lordosis, kyphosis, scoliosis or some combinations of these postures may be developed.
Pelvic stability affects shoulder mobility which gives wheelchair users weight-bearing and movement. Wheelchair users have to perform tasks during the day in a seated posture and the seating for each task performance is not same all day long. Therefore, seating should allow for changes of posture.
An adjustable backrest is an important feature in different conditions to provide adequate trunk support. While propelling a wheelchair uphill or downhill on a ramp, the wheelchair user should lean into the ramp to minimize the risks of injury or feelings of instability. The adjustment of backrest angle will help to open the hip angle to make users dress easily in the wheelchairs. Also, people could have their own preference for the postures in daily activities. Based on the increasing number of wheelchair users, providing an adjustable backrest is necessary because of the importance of seating position and appropriate trunk support.
A backrest has different characteristics according to height, shape, stiffness, weight, adjustability and so on. Based on the height of the backrest, wheelchair users have different support and functions. Low backrest provides freedom of movement, but less stable. On the other hand, high backrest provides more support, but limits mobility for propulsion. The rest of characteristics are different from types of backrests. Manual wheelchairs are commonly fitted with one of three types of backrest: sling upholstery backrest, rigid backrest, and custom molded backrest. Most manual wheelchairs come with sling upholstery for the backrest. The sling upholstery backrest is made of fabric or leather. The rigid backrest is one of the most recommended backrest to support user's posture as a combination of a back cushion on a rigid frame. The custom molded backrest is an individualized backrest for a person who has particular deformity. Each has different perspectives which could be advantages or disadvantages.
The sling upholstery backrest has a rectangular shape based of frames of wheelchair s tubes. The materials of sling backrest which are fabric or leather are stretched out wheelchair backrest. Because of features of materials, it has adjustability, contours to the shape of spine, and is lightweight. An advantage of this type of backrest is that it can be used by a wide range of people because it conforms based on the back shape and posture, and thus it is common and useful. The flexibility of this backrest also makes it ideal for folding wheelchair which is easily transportable. A primary drawback to the sling backrest is that it does not provide a stable base of support for the posture.
The rigid backrest has different features contrast to the sling backrest. The rigid frame of backrest has the contour of back, so it looks a trapezoid from seeing upside. Even though there is cushion on the backrest, the frame is firm and has additional weight. Therefore, it is generally not adjustable and is sensitive to the user's body size. However, it provides a solid base of support for appropriate posture, so it is most appropriate for users without a postural deformity.
The individualized contour backrest is shaped individually, but usually looks big and bulky. This type of backrest covers whole spine and fills spaces to support deformity of spine. It is very individual product, so it requires intensive labor. The quality of the custom molded backrest depends on clinicians' skills.
Among the three types of the backrests, the standard sling upholstery for the backrest has been used for most wheelchair manufacturers and wheelchair users. As mentioned earlier, the sling upholstery has a flexibility and adjustability of tension, so wheelchair users can make periodically suitable. However, it provides less postural support. In addition, it would not be enough to support wheelchair users' back while being in dynamic functions such as up and down ramps, various surfaces and over obstacles.
There is a need for a lightweight, sturdy, user-adjustable, easily set-up and ergonomic backrest support for ultralight wheelchairs to satisfy the needs of wheelchair users by maximizing functionality and improving ease of use. An angle adjustable backrest provides necessary postural support and a variety of positions to easy dressing, propulsion, and seated comfort.